The present invention pertains to a sewing machine with a light barrier and a light source and a light receiver for detecting the edge of a workpiece in the area of the stitch formation site with the light source is connected via an optical light guide to a lens.
A sewing machine with an optoelectronic edge scanning device, in which the light source is connected to a lens via an optical light guide, has been known from DE 35 19 729 C2. An alternative embodiment, in which the light source and the lens are accommodated in a common housing without the interposition of an optical light guide as a light transmitter, is explained in greater detail and represented graphically in the exemplary embodiment of DE-C2. According to the drawing of DE-C2, this light transmitter is arranged in the middle lower area of the front side of the head of the housing. However, there is no free space in this area for the arrangement of the light transmitter at all, because the needle thread coming from the thread take-up lever runs along there.
Other devices and thread guides are known, e.g., with one or more thread-tensioning devices, in which the thread-pulling spring, the thread guide hook and a plurality of thread guide eyelets are arranged on the front side of the head of the housing, besides the thread take-up lever. The space between these devices and guides must remain free for the unhindered movement of the needle thread. The light transmitter is arranged, as is generally usual, either at the edge of the head of the housing or on a laterally extending cantilever bracket, which is in turn fastened to the edge of the head of the housing. If a cantilever bracket is used, the view to the thread-tensioning device may be obstructed and the handling of the thread take-up lever may be compromised during threading.
The basic object of the present invention is to arrange the end section of an optical light guide connected to a light source such that the view to the devices located on the front side of the head of the housing is not obstructed, nor is the handling of the thread take-up lever compromised during threading.
According to the invention, a sewing machine with a light barrier is provided comprising a light source and a light receiver for detecting the edge of a workpiece in the area of the stitch formation site. The light source is connected via an optical light guide to a lens. The lens is arranged in the head area of the sewing machine. A thread guide hook is located in the vicinity of the thread-tensioning device and is designed as a small tube. The optical light guide is led through the thread guide hook. The lens is arranged on the obliquely downwardly directed free end of the thread guide hook.
The lens may be accommodated in a threaded sleeve arranged adjustably on the thread guide hook.
Due to the thread guide hook being designed as a small tube and to the optical light guide being arranged within this small tube, a component of the sewing machine which is present anyway is used with the thread guide hook as a bracket for the end section of the optical light guide and the lens, so that there are no problems here whatsoever concerning the free view to the devices and thread guides located on the front side of the head and there are no difficulties concerning the free access to these components.
The present invention will be explained on the basis of an exemplary embodiment shown in the drawing.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawing and descriptive matter in which a preferred embodiment of the invention is illustrated.